This invention relates to gas burners and gas burner head configurations. More specifically, the invention relates to gas burners of the type typically used in water heaters.
Gas burners for domestic water heaters typically utilize burner heads formed from two concave halves which are secured together. See, for example, U.S. Pat. Nos. 3,992,137; 4,372,290 or 5,335,646. Such burners generally are supported by a bracket attached to the bottom concave portion which includes a central opening for inflow of an air-gas mixture. A plurality of burner ports are disposed in a spaced apart circular array around the periphery of the burner so that a ring of flames issues radially outwardly therefrom for heating the bottom wall of a water tank.
The combustion products of the heating process ideally would consist of carbon dioxide and water. However, if incomplete combustion occurs, carbon monoxide may be produced. Also, at elevated temperatures, a small amount of undesirable nitrogen oxide varieties such as nitric oxide (NO) and nitrogen dioxide (NO.sub.2), generally collectively referred to as NO.sub.x. Nitrogen dioxide, in particular, is objectionable because it is a brownish colored toxic gas which can support combustion. It is desirable and mandated by law that the NO.sub.x species be converted as efficiently as possible to gaseous nitrogen or other nontoxic forms. It has thus remained an ongoing goal of the industry and, in many places mandated by law to produce burners achieving higher combustion efficiency as well as minimization of NO.sub.x content of the exhaust gases.
Briefly, a gas burner of this invention is adapted to discharge fuel at its periphery for combustion. The burner includes upper and lower concave plates secured together to define a chamber and an outer periphery having a plurality of burner ports. The peripheral edge of the top plate is spaced radially outwardly from the central axis a distance beyond the location of the burner ports and into the path of burning gases issuing radially outwardly from the ports, whereby the temperature of said burning gases is reduced thereby reducing the NO.sub.x content of the gases.